Lightweight absorption-dominated electromagnetic interference (EMI) shielding materials are more attractive than conventional reflection-dominated counterparts because they minimize the twice pollution of the reflected electromagnetic (EM) wave. Here, porous Ti2CT x MXene/poly­(vinyl alcohol) composite foams constructed by few-layered Ti2CT x (f-Ti2CT x ) MXene and poly­(vinyl alcohol) (PVA) are fabricated via a facile freeze-drying method. As superior EMI shielding materials, their calculated specific shielding effectiveness reaches up to 5136 dB cm2 g–1 with an ultralow filler content of only 0.15 vol % and reflection effectiveness (SER) of less than 2 dB, representing the excellent absorption-dominated shielding performance. Contrast experiment reveals that the good impedance matching derived from the multiple porous structures, internal reflection, and polarization effect (dipole and interfacial polarization) plays a synergistic role in the improved absorption efficiency and superior EMI shielding performance. Consequently, this work provides a promising MXene-based EMI shielding candidate with lightweight and high strength features.

Two-dimensional (2D) few-layered TiCT MXene (f-TiCT ) has been proved to be one of the most promising electromagnetic interference (EMI) materials, but its electromagnetic (EM) absorption properties and loss mechanism have not been studied so far. Herein, for the first time, ordered lamellar f-TiCT /SiCnws hybrid foams with ultralow density are synthesized by a combination of self-assembly and bidirectional freezing processes. The freestanding foams exhibit excellent EM absorption properties superior to most of the current foam-based counterparts. The effective absorption bandwidth is always able to cover the whole X-band, when the sample thicknesses of f-TiCT /SiCnws hybrid foams distribute in any value between 3.5 and 3.8 mm, and the minimum reflection coefficient reaches -55.7 dB at an ultralow density of only about 0.029 g·cm. The fundamental mechanism associated with optimized impedance matching, enhanced polarization loss, and conductive loss is discussed in detail. Our results evidence that 2D flexible f-TiCT MXene has great potential in EM absorption field like graphene.

No abstract

This paper presents a study on controlling the out-of-water motion of amphibious multi-rotor UAVs using a cascade control method based on the Active Disturbance Rejection Control (ADRC) algorithm. The aim is to overcome the challenges of time-varying model parameters and complex external disturbances. The research involves developing an underwater dynamic model and analyzing hydrodynamic forces to calculate theoretical inertial hydrodynamic forces and simulate viscous hydrodynamic forces. This establishes the relationship between viscous hydrodynamic forces and exit velocity. A complete air dynamic model is then established, selecting model parameters based on the center of mass position of the amphibious vehicle to enable switching from water to air. To address control algorithm instability caused by changes in model parameters, position and attitude controllers are built using the ADRC algorithm. The control effects are compared with traditional PID and sliding mode controllers (SMC) to verify the effectiveness and superiority of the proposed cascade ADRC control strategy. Experimental results show that our controller has stronger anti-interference than traditional PID and SMC controllers and can overcome control instability caused by changes in model parameters. Our research highlights the importance of using ADRC-based controllers for amphibious multi-rotor UAVs to achieve robust and stable control.

Three-dimensional chiral materials with intrinsic chirality play a crucial role in achieving a strong chiral response and flexible light manipulation. Reconfigurable chirality through the 3D morphological transformation of chiral materials is significant for greater freedom in tailoring light but remains a challenge. Inspired by the unique 3D morphological memory capability of shape memory alloys (SMAs), we demonstrate and discuss a chiral resonator in the microwave regime that can realize reconfigurable chirality through 3D morphological transformation. The introduction of heating film realizes voltage control of SMA’s morphology for utilizing the temperature sensitivity of SMA better, enabling arbitrary control of circular dichroism (CD) flip and CD intensity. The qualitative and quantitative analysis of the surface current distribution of chiral enantiomers reveals that the chirality of meta-atoms originates from the surge of electric dipole p x and electric quadrupole Q. It is worth mentioning that the proposed strategy to achieve reconfigurable chirality using 3D morphological transformations can be directly extended to other higher frequencies, such as visible, infrared, and terahertz bands. Significantly, our paradigm to study the relationship between complex 3D morphology and chirality holds potential for application in biosensing, spin detection, and spin-selective devices.